Author: (Linnaeus, 1758)
A slender, long-nosed houndshark with vestigial anterior nasal flaps, large horizontally oval eyes with internal nictitating lower eyelids, subocular ridges obsolete, an arched mouth, moderately long upper labial furrows that fall short of lower symphysis, bladelike compressed teeth with oblique cusps and distal cusplets in both jaws, second dorsal fin much smaller than first and about as large as anal fin, and an extremely long terminal caudal lobe about half the dorsal caudal margin.
Snout moderately long and parabolic in dorsoventral view, preoral length about equal to mouth width; eyes horizontally oval and lateral, subocular ridges obsolete; anterior nasal flaps vestigial, formed as small, low, angular points, well separated from each other and mouth; no nasoral grooves; internarial width over 2.5 times nostril width; mouth broadly arched and long; labial furrows moderately long, uppers ending well behind level of upper symphysis; teeth bladelike, compressed, and cuspidate, similar in upper and lower jaws, anteroposteriors with oblique cusps and cusplets; medial teeth well differentiated from anteroposteriors. First dorsal fin moderately large, base half length of dorsal caudal margin or less; its origin over or slightly behind pectoral free rear tips, its midbase slightly closer to pectoral bases than pelvics; second dorsal much smaller than first, less than half height of first; anal fin about as large as second dorsal; ventral caudal lobe strong in young and adults; terminal lobe of caudal fin long and about 2 times in dorsal caudal margin.
Western South Atlantic: Southern Brazil to Argentina. v Eastern Atlantic: Iceland, Norway, Faeroe Islands, British Isles to Mediterranean and Senegal, ? Ivory Coast, ? Nigeria, ? Gabon to Zaire, Namibia to South Africa. Western Indian Ocean: South Africa. Western South Pacific: Australia (Western and South Australia, Victoria, Tasmania, New South Wales, southern Queensland), Lord Howe Islands, Chatham Islands, New Zealand. ? Central Pacific: Laysan Islands. Eastern Pacific: British Columbia to southern Baja California, Gulf of California; Peru and Chile.
Habitat and Biology:
An active, strong-swimming, abundant, coastal-pelagic species of temperate continental and insular waters, often found well offshore (but not oceanic) as well as at the surfline, in shallow bays, and in submarine canyons; often occurs near the bottom, at depths of 2 to 471 m. It is best known and is very abundant in cold to warm temperate continental seas, and tropical records of the species (particularly off West Africa but also Laysan Island) need to be confirmed and may be based on some other species (off East Africa, possibly based on Hypogaleus heugaensis). It apparently occurs in small schools that are highly migratory in higher latitudes in their range, in some places moving poleward during the summer and equatorially in the winter (European waters and the eastern North Pacific, and southern Australia in part), or into deeper offshore waters in winter longitudinally in other areas (southern Australia in part). They can move swiftly, up to 56 km per day, and have been recorded as moving 1600 km at sustained rates of 16 km a day.
At least in some areas there is pronounced partial segregation by size and sex. In Californian waters during the pre-second world war soupfin fisheries there was a gradiation from predominance of adult males to predominance of adult females from north to south, with equal numbers of both sexes off central California; exceptions included San Francisco and Tomales Bays in northern California, when used as pupping grounds by adult females along with more important southern California inshore areas. The largest males occurred in northernmost waters. Adult males favour deeper waters while females occur closer inshore. In Australian waters schools have been found to be narrowly size and sex related, with those of yearling juveniles ranging into more estuarine situations than older juveniles and adults (except for pupping females). Off southeastern Australia sharks increase in size frequency from east to west from eastern Bass Strait to South Australia, and also increase off southern Tasmania, indicating a gradiation of higher numbers of adults westward and southward.
Population dynamics of the school shark has been studied in great detail off southeastern Australia. These are throught to be a different stock or population from school sharks off Western Australia. In summary, pregnant females move into shallow, partly enclosed bays and estuaries in late spring and early summer, and depart after dropping their young to offshore feeding grounds. Most young of the year depart the pupping grounds in late summer and move offshore, but mostly return to the bays and estuaries of their birth the following spring; some juveniles may switch to adjacent bays and estuaries. Some juveniles may remain in an estuary for up to two years before departing. Juveniles two years old join schools of immature sharks that are inshore or offshore along the coast. Schools of adult sharks inlate summer and winter move either to deeper waters at the edge of the continental shelf in the Bass Straits region, or to warm waters of South Australia and New South Wales; at the edge of the shelf copulation occurs. Adult sharks then travel southward and shoreward in the spring to converge along the coastlines, where they feed in schools that vary their composition of individuals. About half of all adult females in these schools may be pregnant during the breeding season, and these visit the pupping grounds to renew the cycle.
Ovoviviparous, without a yolk-sac placenta; number of young 6 to 52 per litter, increasing with the size of the mother and averaging greater in the eastern North Pacific soupfin (in which the size at maturity and maximum size is greater, mean about 35) than in Australian school sharks (28) or European topes (possibly less than 20). Australian school sharks are recorded as producing litters with more males than females (54:46), but in two-year-old juveniles the ratio of males to females is reversed, apparently from increased mortality of males for unknown reasons. In school sharks the growth rate is regular and apparently does not show much seasonal variation. Male Australian school sharks mature at over 8 years old and mate at about 9 years, while females mature at at least 11 years old and give birth when at least 12 years old; the life expectancy of a large female school shark is at least 22 years.
Preys heavily on bony fishes, taking a wide variety of bottom and schooling midwater fishes including pilchards, herring, sardines and other clupeids, anchovies, salmon, smelt (Osmeridae), Australian whitebait (Aplochitonidae), hake, cod, ling and other codlike fishes, midshipmen, flyingfish, barracouta (Gempylidae), mackeral and small tuna, barracuda (Sphyraenidae), croakers, wrasses, opaleyes (Girella), surf perches (Embiotocidae), da mselfishes, gobi es, kelpfish (Clin idae), so le, halibut and other flatfish, rock fish and scorp ionfish, sculpins, sablefish, but also cephalopods (most importantly squid, but also octopi), marine snails, crabs, shrimp, lobsters, annelid worms, echinoderms, and uncommonly other chondrichthyians (ratfish, sharks and small stingrays and skates). Although primarily an opportunistic predator on moderate-sized bony fishes (taken alive), this shark readily feeds on some invertebrates; young sharks may take more invertebrate prey than adults, and in some areas crabs and squid may be important prey items. This shark is little inclined to scavage, however, judging from the virtual absence of garbage and meat from terrestrial and large marine mammals in its reported diet (unlike the largely sympatric spotted sevengill shark, Notorynchus cepedianus, which readily eats such fare), as well as its strong preference for very fresh fish or squid bait over slightly stale or even fresh-frozen bait presented on hooks.
Although moderately large and active, the tope shark has never been reported to attack people. It will, however, snap when captured and has sufficiently large teeth to invite respect. On the other hand, the main enemy of this shark is undoubtedly Homo sapiens, particularly through wanton slaughter of juvenile sharks by misguided sports and commercial fishermen and killing of pregnant females. Natural predators of this shark include more powerful predatory sharks found in temperate waters, such as the great white shark (Carcharodon carcharias) and possibly the spotted sevengill shark (Notorynchus cepedianus), and probably marine mammals. If not badly traumatized in capture this shark will readily survive in large aquaria as in the Port Elizabeth Oceanarium, South Africa.
Maximum 195 cm (large females of the eastern North Pacific form); males maturing between about 120 and 170 cm and reaching a maximum of 155 to 175 cm, females maturing between about 130 and 185 cm and reaching a maximum of 174 to 195 cm (combined figures for Californian, South African and Australian G. galeus); young born at about 30 to 40 cm long.
Data from California soupfin sharks (Ripley, 1946) indicates that there is an allometric change in length/weight relationships in adult females but possibly not for males. Logarithmic length/weight curves given by Ripley (1946) indicate log Wt (Ibs) = -5.573 + 3.2.701og total length (cm) for female soupfin 40 to 149 cm but jumping to log Wt (Ibs) = -7.490 + 4.156 log total length (cm) for females 150 cm and larger (N = 869); for males (N = 42) this is log Wt (Ibs) = -5.411+ 3.186 log total length (cm). For males and immature females, weight increases at slightly more than the cube of the length, indicating a retention of the slim build of young sharks, but as females mature they become relatively stockier and grow at over the 4th power of their length. Olsen (1954), with a smaller sample (254) for females and larger one for males (278) suggested that for the Australian school shark there was no such change in females, but his plot of female length/weight relations (Olsen, 1954, fig. 3), suggests that females above 135 cm may be dbeparting the curve calculated for all females (which is almost the same for that of males, Wt (Ibs) = 4.86 x 10 total length exp 3.18; males, Wt (Ibs) = 4.80 x 10 total length exp 3.17).
Interest to Fisheries:
This species is an important shark for fisheries, especially off Uruguay and Argentina, California, and southern Australia, but it is also fished elsewhere where it occurs. Its meat is excellent for human consumption and is eaten fresh, fresh frozen, or dried salted; its liver contains oil that is extremely high in vitamin A; and its fins are used for sharkfin soup. It is caught with bottom and pelagic gillnets, bottom and pelagic longlines, bottom and pelagic trawls, and with hook-and-line. A large fishery for this species existed off California in the thirties and fourties, which peaked at 4186 tons landed in 1939 but declined with overfishing and the substitution of synthetic vitamin A for that extracted from shark liver oil. A very similar fishery existed off South Africa at about the same time as the Californian fishery, and went through a similar cycle of growth and collapse. Currently these sharks are the object of an expanding commercial and sports fishery for human food off California, but stocks are already showing some signs of depletion there. It is doubtful whether stocks off California have in recent years attained the size of those exploited before the second world war. Fisheries in Australia and New Zealand have been restricted or have collapsed due to findings of high mercury levels in school sharks caught there. Topes figure prominently in a South African fishery centred in Gans Bay, and are processed for vitamin oil, fins, and "biltong" or dried meat.
Topes are also a common and popular catch of sports anglers, being commonly taken by rod and reel particularly in the British Isles, off South Africa and California. This shark will fight actively when hooked, but is currently not considered a game fish by the International Game Fish Association.
Important Regional Names:
Tope shark (British Isles); Vitamin shark (Uruguay and Argentina; Tiburón vitaminico); Soupfin shark (California to British Columbia, also South Africa); School shark (Australia and New Zealand).
Holotype: Unknown. Type Locality: "Habitat in Oceano Europae".